Drilling fluids have been used since the very beginning of oil well drilling operations in the United States and drilling fluids and their chemistry have been and remain an important area for scientific and chemical investigations. Certain uses and desired properties of drilling fluids are reviewed in U.S. Patent Application Publication No. 2004/0110642 and U.S. Pat. Nos. 6,339,048 and 6,462,096, issued to the assignee of this application, the entire disclosures of which are incorporated herein by reference.
Nevertheless, the demands of the oil-well drilling environment require increasing improvements in temperature stability. This becomes particularly true, for example, as the search for new sources of oil involves greater need to explore in deep water areas and to employ horizontal drilling techniques.